Chrysolina americana

(Linnaeus, 1758)

The only member of the subgenus Taeniochrysa Bechyné, 1950 this very distinctive beetle is native to Southern Europe, North Africa, The Near East and The Middle East. It is locally common throughout its range occurring in sparsely vegetated or lightly wooded areas on sandy soils where the host plants occur. Hosts are various aromatic Lamiaceae including Rosemary, Lavender and Thyme; both adults and larvae consume the foliage but the species is not generally considered a pest. Eggs are laid on the host foliage in late summer and larvae develop through the winter, pupating in the soil in the spring. The adults eclose after about three weeks and feed into early summer before an aestivation period during the warmest months. The first U.K. record was from Cheshire in 1963, it was then discovered at RHS Wisley in 1994 and has since spread rapidly; by 2002 it was widespread around London and it now occurs across the southeast, and there are scattered records through England, Wales and Southern Scotland. Here it occurs on the hosts in gardens, parks, nurseries and amenity planting in any situation. The adults occur throughout the year; in Watford they are active through the winter and, as elsewhere, often occur in large numbers which persist for several years. The biology is much the same as in its native range with eggs laid in the autumn and larvae developing from January or February, four instars are passed and development may be as brief as three weeks, fully grown larvae enter the soil and form a cell where the prepupal and pupal stages are passed. New generation adults appear in May and June, swelling the numbers of those that have overwintered so that at this time they may be particularly abundant. The numbers tend to decrease during the summer, although they remain obvious throughout the season, and increase again in the autumn.

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Adult length 6.7-8.1mm. This species is distinctive among the U.K. fauna due to the contrasting longitudinal stripes of colour on the elytral interstices; the only other species to display this colouration is C. cerealis but the present species is distinct in having well-formed elytral striae which are arranged in double rows, pale appendages and a smooth and shiny pronotal disc which is only very finely punctured and microsculptured (X40).